Personal knowledge distinguishes groups differently than primary-secondary divides do.

Evidence

These two sets of distinctions (personal knowing I categoric knowing; personally-known others/strangers) are similar but not identical to the traditional sociological scheme for classifying forms of human association: primary group or relationship /secondary group or relationship. Primary groups are certainly groups made up of persons who have personal knowledge of one another. But these persons also have categoric knowledge of one another. Primary groups are clearly groups of personally-known others, but so, in the main, are secondary groups. The fact that secondary relationships may be characterized as “formal, impersonal and institutional” (E. Faris, 1932 :46) does not at all imply that these are relationships between “strangers,” at least not in the sense in which I am using the term. — Lyn H. Lofland, World of Strangers_ Order and Action in…, 1076

Categorization

• DEFINE: Clarifies that the personally-known/categoric-knowing axis is cognitive, cutting across primary/secondary group categories rather than mapping onto them. Useful for the reader’s analysis of urban stranger-relations.
• XREF: Complements Simmel’s blase attitude and Lofland’s stranger-type categories; clarifies where Lofland’s own typology diverges from standard sociology-of-groups schema.